Button and dovetail connector actuation mechanism

ABSTRACT

A connector for joining a printed circuit board (202) having an army of contact pads (204) to a connector (200) incorporating flexibe circuits (210) with mating contact pads (212), by means of a button and dovetail type interaction between the board and connector. A post (206) projects from the surface of the board. Each post has an enlarged head so that the post resembles a button. The head, when mated with a slot (220) on the connector, achieves a camming action resulting in a predetermined normal force versus insertin position relationship. A compliant member (224), preferably a fluid filled bladder, is supported by a beam member (208) and interposed between the beam member and the array of flexible circuit contact pads. A dovetail slot provided in the beam member is shaped to receive the corresponding post and has a precisely shaped cam race surface which engages the head of post. Such arrangement urges the contact pads on flexible circuit against the mating contact pads on the printed circuit board.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is the national stage of International Application No.PCT/US97/11101 filed Jun. 26, 1997, and the regular application under 35U.S.C. § 119(e) of provisional application No. 60/020,888 filed Jun. 28,1996. This application claim benefit to provisional application60.020,888 filed Jun. 28, 1996.

BACKGROUND OF THE INVENTION

The present invention relates to connectors for electrical conductors,and more particularly, to connectors for joining high density conductorssuch as found on printed circuit boards, with corresponding contacts onflexible circuits.

As the size and/or complexity of circuit components and their associatedprinted or etched circuit conductors continue to be miniaturized, thesize of the contacts for interconnecting components has also decreased.Conventional spring biased connectors can no longer be effectively usedunder these circumstances. U.S. Pat. No. 4,968,265, issued Nov. 6, 1990for "Fluidly Actuated Electrical Connector", and U.S. Pat. No.5,002,496, issued Mar. 26, 1991 for "Cam Actuated Electrical Connector",represent significant improvements to earlier connectors, byestablishing and maintaining electrical contact between conductivemembers to be joined, without inherent minimum line and spacelimitations that depend upon the spring characteristics of the matingcontact structures. These patents describe the implementation ofso-called "hydrostatic connector" techniques, which utilize a fluidbladder interacting between a backing member and the conductors, wherebythe bladder forms a compliant membrane surface that transmits forceuniformly from the backing member to the flexible circuit, forcingcontact pads on the flex circuit to mating pads on the PCB such that ahigh integrity electrical connection is realized. The disclosures ofthese two patents are hereby incorporated by reference.

Although the various embodiments described in the patents mentionedimmediately above, can perform satisfactorily, the actuation mechanismsare not well integrated with the connector, resulting in a significantincrease in manufacturing costs, as well as occupying space which couldotherwise be utilized for further miniaturization and compacting ofcomponents.

Some efforts have been made to improve these deficiencies, asrepresented by the Hydro Flex™ connector system from SynapseTechnologies, Inc. This system is made up of two functional parts, acontrolled-impedance flex circuit with ground-plane, gold contact pads,and a molded beam force generator containing a sealed, fluid-filledbladder. When actuated, the beam is deflected and the bladder forcespads on the flex circuit against mating pads on e.g., a PCB, providinguniform normal force and virtually zero shear force. This connectorsystem is tolerant of variations in board thickness and flatness, andmaintains a gas tight seal over a wide temperature range. Contactdensities of up to 100 per inch are achieved on a single sided stackingconfiguration, and up to 200 per inch in a double sided right angleversion. Although the actuation scheme in the Hydro Flex™ connector wassimplified relative to that disclosed in the two patents identifiedabove, the technique for actuating the beam to energize the bladderagainst the pads on the flex circuit and against pads on the PCB, didnot allow contact pad wipe.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provideapparatus and method for actuating a hydrostatic connector in the field,which wipes the contact pads while eliminating the negative impact ofcontamination and/or oxidation, and allows establishment of highquality, low resistance electrical connections.

It is another object of the invention, to provide a connector system,wherein a predetermined normal force between conductors to be mated isachieved as a result of a predetermined force versus positionrelationship generated as the connector and, for example a printedcircuit board, are moved toward each other.

It is yet another object of the invention to provide a connector system,whereby such a pre-established normal force versus position relationshipcan be achieved, independent of the thickness of the printed circuitboard or the like, to which the connector is joined.

It is yet a further object of the invention, to provide a connectorconstruction, wherein a pre-curvature in the shape of the connector,overcomes certain anomalies that have been observed in known connectors.

Additionally, the invention achieves the primary objectives with a verysimple mechanism made up of components which are readily manufacturedand inexpensive, while retaining all of the previously demonstratedbenefits of hydrostatic connector technology.

These objects are achieved by providing a connector actuation mechanismfor joining a circuit-carrying substrate such as a printed circuit boardhaving an array of contact pads on one or both surfaces, to a connectorincorporating one or more conductor leads, such as flexible circuitswith mating arrays of contact pads, by means of a button and dovetailtype interaction between the board and connector. A post rigidlyprojects from the surface of the board on either end of the boardcontact pad array. Each post has an enlarged head, so that the postresembles a button. The head has a predetermined geometry which, whenmated with a dovetail-like slot on the connector, achieves a cammingaction resulting in a predetermined normal force versus insertionposition relationship. The connector carries a beam assembly whichincludes a beam member extending transversely behind the array of flexcircuit contact pads. A compliant member, preferably a fluid filledbladder, is supported by the beam member and interposed between the beammember and the array of flexible circuit contact pads to provide forcedistribution and equalization for the array of contact pads. A dovetailslot is provided in the beam member on either end of the flexiblecircuit contact pad array. Each slot is shaped to receive acorresponding post. The slot has a precisely shaped cam race surfacewhich engages the head of the post. Such engagement at each end of thebeam member, pulls the ends of the beam toward the printed circuitboard, at a controlled rate, which urges the contact pads on theflexible circuit against the mating contact pads on the printed circuitboard. The slots and posts are located such that they achieve andmaintain alignment between the pads on the flexible circuits and themating pads on the printed circuit board.

Preferably, the predetermined force versus position relationshipincreases to a relative maximum force as the connector is engaged, anddecreases to a lesser value at the fully engaged position, therebyachieving positive retention of the connector in the engaged position.The connector actuation is independent of the thickness of the printedcircuit board, and is defined solely by the relative positions of thepost heads and mating slots in the beam assembly.

In a particularly noteworthy feature, which can be implementedindependently of the button and dovetail type actuation, the beam memberis molded with an inherent curvature, such that the bladder retained inthe beam, has a convex curvature relative to the PCB, at initiation ofthe actuation. Upon completion of actuation, the beam and associatedbladder are flat. The precurve in the beam according to this feature,allows maintenance of a constant separation of the beam from the back ofthe flexible circuit, minimizing deformation of the bladder which canarise due to temperature cycling and other environmental effects, afterthe connectors have been in service for some time.

In method form, the invention is implemented by joining a printedcircuit board or the like having an array of conductors to a connectorhaving a flex circuit or the like with a corresponding array ofconductors, by providing at least two posts each having a cam profile,on one of the board or connector, and providing a respective two slotseach defining a cam race, on the other of the board or connector. Theposts and slots are advanced toward each other such that upon partialengagement between the posts and slots, the conductors on the boardcontact respective conductors on the connector. Upon continuing advanceof the posts and slots toward each other, the cam profile on each postinteracts with the cam race on a respective slot to produce apredetermined normal contact force versus advancing positionrelationship between the conductors in contact, whereby at a fullyengaged position of the posts and slots the normal contact force issufficient to enable signal transmission through all conductors incontact, with negligible deterioration.

BRIEF DESCRIPTION OF THE DRAWINGS

The preferred embodiments will be described below with reference to theaccompanying drawings, in which:

FIG.1 is a schematic representation of a printed circuit board having apost, and a connector having a slot, to illustrate the basis of thepresent invention;

FIGS. 2(a) and 2(b) represent opposed electrical contact pads duringinitiation and completion of the actuation of the connector according tothe invention;

FIGS. 3(a) and 3(b) represent different stages during the actuation ofthe connector according to the invention;

FIG. 4 is a longitudinal section view of a post suitable for use withthe present invention;

FIG. 5 is a graph showing a representative relationship of the normalforce per contact pad, versus insertion distance of the post into theslot along cooperating cam surfaces, in accordance with the invention;

FIG. 6 is a schematic view, similar to FIG. 1, showing additionaldetails of one implementation of a suitable slot configuration for usewith the present invention;

FIG. 7 is an exploded view of one implementation of the invention, bywhich two printed PCBs can be connected to a respective two connectors,in close parallel relation;

FIG. 8 shows the completed connection corresponding to the exploded viewof FIG. 7;

FIG. 9 shows an alternative connection, by which two PCBs are mated withcorresponding connectors at right angles to each other; and

FIGS. 10(a) and 10(b) schematically show another inventive feature bywhich the beam which carries the bladder and has the slots at eitherend, is formed with a precurve which straightens during actuation.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a connection 10 about to be made, between a printed circuitboard (PCB) 12, which has an array of conductor leads 14 on one surface16, and a portion of a connector 18 adapted to support a correspondingarray of flex circuit conductors (which in the illustrated embodimentwould be on the underside 20, and therefore are not visible). Theconnector can optionally be supported directly or indirectly by achassis (not shown) in an electronic system such as a computer, processcontrol system, or the like.

FIGS. 2(a) and 2(b) illustrate in a detailed enlargement, the manner inwhich the conductor leads 14 from the PCB, are to mate withcorresponding flex circuit conductors 26 on the connector, as the PCB 12is joined to the connector 18, in a manner to be more fully describedbelow. The conductors 14 terminate in contact pads 24 and the conductors26 likewise terminate in contact pads 28. At initialization of themakeup of the connection, represented in FIG. 2(a), the pads 24, 28would ideally overlap with a slight spacing between them at 30. This isnot absolutely necessary, in that the overlap could be achieved with avery low force, so long as the pads 24,28 do not abut end-to-end. Uponcompletion of the makeup of the connection, as represented in FIG. 2(b),the pads 24,28 are fully overlapped at 32, and there is established anormal force between the pads sufficient to ensure negligibledeterioration of the signals to be transmitted through the pads, duringoperation of the equipment in which the connection has been made. Awiping action between pads is achieved as a result of the actuatingsequence described below.

With reference now to FIGS. 1-3, a rigid post 34 projects from surface16 of the board 12, on either side of the array 14, to mate with thecorresponding slots 40 in the beam 38 which is part of the connector 18.

Each post 34 includes an enlarged head 36. The slot 40 in the beammember on either side of the array of flex circuit conductors on theunderside 20, are shaped to receive the corresponding posts 34 along adirection transverse to the beam member 38. Each slot has a rigid camrace 42, for engaging a cam profile 44 on the head of the post. As theboard 12 is moved toward the connector 18, the posts 34 enter respectiveslots 40 and the cam profiles 44 on the heads follow predetermined pathsalong the cam races 42, thereby pulling the ends of the beam, where theslots are located, downwardly In the direction of the PCB at acontrolled rate dictated by the relationship between the cam profile 44and cam race 42. In FIG. 3(a), the initial contact of the pads accordingto FIG. 2(a) is represented at 30, and the completion of the actuationis represented in FIG. 3(b), whereby the pads are fully overlapped withthe desired normal force therebetween, according to FIG. 2(b).

It can be appreciated from FIG. 1, that the extent to which theconnector 18 and board 12 are drawn closer together, depends on therelationship between the force exerted between the cam profile 44 andcam race 42, versus insertion position of the post 34 in the slot 40.Whereas the connector 18 including beam 38, slot 40 and cam race 42 canbe manufactured with a high degree of care and uniformity, particularlyif they are manufactured under the authority of a single source, such ahigh degree of dimensional control cannot be expected with regard to thethickness of the PCB 12, with can typically vary plus or minus 10%. Thevariation on the PCB thickness does not, however, present a concern withthe present invention, because the height and shape of the post 34,relative to the surface 16 of the PCB 12, can be specified andcontrolled with a much higher degree of accuracy. In other words, theprofile of the post 34, as shown in FIG. 4, can be easily controlledwith respect to the height dimension shown in FIG. 1, relative to thePCB surface 16. The surface 16 serves as a datum unique to each PCB,regardless of the PCB thickness. In particular, it can be seen in FIG. 4that the head 36 has a substantially frustoconical underside definingthe cam profile 44. By "frustoconical" in this context, is meantobliquely outward from the vertical. The cam profile 44 when viewed asin FIG. 4, need not be straight, but can be radiused with one or morecenters of curvature.

The Interaction of the cam profile 44 with the cam race 42 as describedabove, permits the design of a connector system which can be furtherspecified and controlled as shown in FIGS. 5 and 6. FIG. 5 shows a curveof the normal force per contact pair (i.e., as shown in FIG. 2(b)),versus the insertion distance of the cam profile 44 along the cam race42, as represented in FIGS. 1 and 3. As an example, but by no meanslimiting in its implementation of the present invention, if thedisplacement between the position shown in FIG. 2(a) and 2(b) is 0.03inch, the desired normal force along that insertion distance isrepresented by curve 46. This curve is substantially linear duringapproximately 60% of the insertion travel, then rises to a maximum at48, before decreasing to the full insertion position at 50. The curveportion between 48 and 50, monotonically decreases. The illustratedshape of the normal force versus insertion relationship, results fromthe desirable property that if the user manually moves the PCB into theconnector through the insertion distance, the head "snaps" at themaximum 48 to define the final position 50, and is retained there unlessa positive retraction force is applied in the reverse direction upportion 52 of the curve.

The characteristics of curve 46 for which a particular connector systemwill be designed, depend on for example, the material of the contactpads, the pad geometry, the uniformity of the contact pads, and thelike.

This degree of control on the normal force versus insertion, depends notonly on the design and care in the fabrication of the cam profile 44 onthe post, but also on the ease with which the cam race 42 can beprovided in the beam. FIG. 6 shows a variation 100 of an arrangementthat generally resembles that shown in FIG. 1. The PCB 102 has an uppersurface 104 on which an array of leads with contact pads spans theregion generally indicated at 106. For convenience, a directionalreference coordinate system is shown at the left of FIG. 6. The leadingedge of the PCB 102 is parallel to axis X, the PCB is moved in directionY to make up the connection, and as the connection is made, the surface104 and the connector beam 114, move toward each other along axis Z.Each conductor lead in array 106 typically extends along direction Y, asdo the flex circuit conductors beneath beam 114. The beam 114 extendsalong direction X, transversely behind the array of flex circuitconductors, The connection according to the invention can be mademanually, without the aid of a tool. Alternatively, the connector couldbe actuated in an electrical system chassis having mechanical assist ofa type similar to what is conventionally available.

In the embodiment of FIG. 6, the POB 102 has through holes 108 on eitherside of the array 106, for receiving respective dual post members110,112, which interconnect through the holes 108, for example, bythreading or riveting. This connection is completed when the rim orshoulder 111 contacts the corresponding surface 104 of the PCB, therebyestablishing the datum for the distance of the cam profile on the head,relative to the surface 104 of the PCB. Such a shoulder can also beprovided on the opposed post component 112, whereby a similar datum isestablished for the projection of post portion 112 from the other sideof the PCB 112.

The slots 116 at each longitudinal end of the beam 114, extend in the Ydirection, and in the illustrated embodiment, intersect with a cut out118 extending downwardly along the Z direction. The cut out has aninternal ledge 120, which is substantially U-shaped at a predetermineddistance along the Z direction, from the undersurface of the beam 114that carries the flex circuit conductors. A carefully fabricated clip122 is dropped through cut out 118 onto, for support by, ledge 120. Theclip 122 is preferably metal and generally U shaped, with the openportion 124 situated to receive the head of post 110. The upper surface126 of the clip 122 defines the cam race, and also has a substantiallyU-shape. The cam race could, alternatively, be integrally molded as partof the ledge 120.

This "U"-shape converges along the direction from the open to the closedend (i.e., long direction Y), such that the contact between the cam racesurface 126 and the cam profile 44 (as shown in FIG. 4) moves closer tothe cylindrical stem of the post 34, as the post moves in the insertiondirection Y. This also moves the beam downwardly in the Z direction,relative to the datum surface 104 of the PCB. The clip 122 can divergeslightly as the legs approach the closed end, to provide the snap in andretention property represented at portions 48, 50 and 52 of FIG. 5.

Those of ordinary skill in the field of fabricating precision fixturingand the like, can, from the present description, implement the suitablevariations of the "button and dove tail" actuation scheme describedherein, to meet the specific requirements of end users. Accordingly, theform and shape of the cam profile and cam race described herein, shouldnot be understood as limiting the scope of the meaning of those terms inthe appended claims.

FIGS. 7 and 8 illustrate in greater detail, a practical implementationof the present invention using the principles described above. Theconnection 200 is made in the first instance, between the PCB 202 havingthe conductor array 204, by the engagement of the spaced apart posts 206with the connector beam 208a. In this embodiment, two connectors 226,228 are stacked back-to-back, for receiving two PCB's 202, 230 inparallel, spaced relation. The connector beam 208a has a flex circuit210a secured thereto, such that the array 212a of conductors andassociated contact pads, are situated on the underside of the beam 208a.The lateral or border portions of the flex circuit 210a, have cut-outs218a which align with the slots 220a on the beam. Alignment holes 214 onthe flex circuit 210 can engage corresponding alignment pins 216 on thebeam, to assure correct positioning of the conductor pads in array 212a,relative to the slots 220a and likewise to assure registry with the padson array 204 when the posts 206 on board PCB 202 are fully engaged inthe slots 220a.

Similarly, beam 208b has another portion 212b of the flex circuit 210bwrapped and secured thereto, for alignment and mating with the pads onthe underside of PCB 230. With respect to both beams 208a and 208b, therigid beam member extends transversely behind the array 212a, 212b, ofthe flex circuit conductors. A constant volume, fluid filled bladder 224is supported by the beam 208b (but a corresponding bladder is notvisible in 208a), preferably in a substantially square channel extendinglongitudinally in the beam member. The bladder provides forcedistribution and equalization for the array of contact pads. Upon fullactuation of the connector to the condition represented in FIG. 3(b), auniform normal force is imposed on every pair of mating contact pads,due to the hydrostatic pressure transmitting effect of the bladder.Although a constant volume fluid-filled bladder is preferred, thepresent invention can still be advantageously implemented with anycompliant member, e.g., a strip of rubber.

With particular reference to FIG. 8, it can be appreciated that,preferably, a stabilizing beam with associated bladder, is actuated by abutton and dove tail connection of the present invention, via engagingposts (not shown) projecting from the top surface of card 230. Thisconnected beam would traverse the top of card 230, between the phantomlines indicated at 232. Similarly, another stabilizing beam withassociated bladder would engage with posts projecting from the undersideof PCB 202, as indicated at 234, parallel with the lines indicated at232. Each stabilizing beam and bladder can be identical in structure to208b. In general, it is preferred that, wherever a beam with associatedflexible circuit, is urged against a conductor array on the surface of aPCB, a backing or stabilizing beam with bladder also be secured on theback side of the card, to produce a force against the back side of thecard, in opposition to the force imposed on the side of the card havingthe array, by the other beam.

FIG. 9 represents another embodiment 300, wherein a PCB 302 is mated viaconnectors 306, 310, in a compact configuration adjacent to the matingof another PCB 304 perpendicularly to PCB 302, which is effectuated byconnectors 308, 312. In this embodiment, the connectors 306, 310 exertnormal forces on opposite sides of the card 302, in opposition to eachother, and thereby provide the desired balance. The connectors 308, 312both exert normal forces to the visible side of card 304 and therefore,it is preferred that counter balancing stabilizing beams with bladder beattached to the underside of PCB 304, at 314 and 316.

As discussed above, the hydrostatic nature of the normal forces appliedto the mating pads, resulting from actuation as represented in FIG. 3(a)and (b), assures a uniform force on each pair of contact pads. Uponobserving inexplicable evidence of non-uniformity of contact pressureafter periods of extended use, a further improvement was made which haseliminated this anomaly. As shown in FIG. 10, if the rigid molded beam400 is preformed with a curvature which is convex along the bladder 420(i.e., convex relative to the surface of a PCB 402 with which it willmate), the uniformity of contact pad force does not deteriorate underany circumstances presently known to the inventors. As a result of thecurvature, each longitudinal end 404, 406 of the beam is raised relativeto the surface of the PCB, before actuation. The desired curvature canbe quite small, i.e., on the order of 0.005 inch deviation in a beamhaving a length of a few inches, as indicated at 408. It may bedesirable to include pedestals 410, 412 at each lateral end 404, 406 ofthe beam, substantially under the respective slots 414, 416.

Upon actuation as represented in FIG. 10(b), the beam will be relativelystraight, as will the channel 418 and bladder 420 supported by the beam.The fact that in the actuated condition, the beam is straight, as shownin FIG. 10(b), rather than slightly concave relative to the PCB, shownin FIG. 3(b), is believed to prevent localized extrusion of bladder wallmaterial or other anomalies that were observed after extended use of theequipment in which the connection was made.

What is claimed is:
 1. A connector arrangement for joining a printedcircuit board having an array of conductors spaced in a lateraldirection on one surface, to a connector having a flex circuit with acorresponding array of conductors spaced in said lateral direction,comprising:a printed circuit board including a post rigidly projectingfrom said one surface of the board on each lateral side of the boardconductor array, each post including an enlarged head having a camprofile; a connector beam assembly including,a rigid beam membersituated behind the flex circuit and extending along the lateral spacingdirection of the conductors, a compliant member directly supported bythe beam member and interposed between the beam member and the flexcircuit to provide compliant support for the array of flex circuitconductors, a slot in the beam member on each lateral side of the arrayof flex circuit conductors, shaped to receive a corresponding post, saidslot having a rigid cam race for engaging the cam profile on the head ofthe post, whereby as the board is moved toward the connector, each postenters a respective slot and the cam profile on each head follows apredetermined path long a cam race, thereby urging the board array andthe connector array into contact with each other.
 2. The connectorarrangement of claim 1, herein each predetermined path includes arespective stop position which retains the post in the slot to maintaina predetermined contact force between each of said board conductors anda corresponding flex circuit conductor.
 3. The connector arrangement ofclaim 1, whereineach head has a substantially frustoconical undersidedefining said cam profile, and each cam race has a substantially "U"shape which is open to receive said head, and converges along saidpredetermined path.
 4. The connector arrangement of claim 1, wherein thecompliant member is an elongated fluid-filled bladder extending in saidlateral spacing direction and wherein each slot is shaped to receive acorresponding post along a direction transverse to the bladder.
 5. Theconnector arrangement of claim 1, wherein each slot is defined by arecess in the beam member and a distinct clip member supported in therecess, said clip defining said cam race.
 6. The connector arrangementof claim 5, wherein the cam profile on the head of the post is definedby a substantially frustoconical underside of the head.
 7. The connectorarrangement of claim 6, wherein the compliant member is an elongatedfluid-filled bladder extending in said lateral spacing direction andwherein the slot is shaped to receive a corresponding post along adirection transverse to the bladder.
 8. The connector arrangement ofclaim 3, wherein the board has a leading edge and the slot is shaped toreceive a corresponding post along a direction perpendicular to saidleading edge.
 9. The connector arrangement of claim 1, whereinthe boardhas an opposite surface to said one surface, the opposite surface havingspaced apart posts projecting therefrom, and a stabilizing beam assemblyis situated on said opposite surface, and includes a beam membersupporting a compliant member, and slots which engage said spaced apartposts on said opposite surface, for producing a force against saidopposite surface of the board in opposition to the force which urges theconductor array on said connector toward the board array on said oneside of the board.
 10. The connector arrangement of claim 9, whereineach beam member has a curvature which is convex along the respectivecompliant member prior to actuation, but is flat after engagement of theposts with the slots.
 11. A connector actuation mechanism joining aprinted circuit board having an array of contact pads on a surface to aconnector incorporating one or more flexible circuits with a matingarray of contact pads, comprising:spaced apart posts rigidly projectingfrom said surface of the board, each post including an enlarged headwith a predefined geometry; a connector beam assembly including,a beammember extending behind the arty of flex circuit contact pads, acompliant member supported by the beam member and interposed between thebeam member and the array of flexible circuit contact pads, spaced apartslots in the beam member, each slot shaded to receive a correspondingpost along a post insertion direction and having a predefined cam racesurface for engaging the head of said corresponding post; whereby as theconnector is moved toward full engagement of the slots onto the poststhe connector is pulled toward the printed circuit board according to apredefined pulldown force versus post insertion position relationship,which urges the contact pads on the flexible circuit against the matingcontact pads on the printed circuit board.
 12. The connector actuationmechanism of claim 1 , wherein the slots and the posts are located suchthat they achieve and maintain alignment between the pads on theflexible circuits and the mating pads on the printed circuit board. 13.The connector actuation mechanism of claim 11, wherein the predeterminedforce versus position relationship goes through a maximum pulldown forcebefore the posts and slots are fully engaged, thereby achieving positiveretention of the posts in the slots.
 14. The connector actuationmechanism of claim 11, wherein the pulldown force versus post positionrelationship is dependent on the positions of the post heads in theslots, and is independent of the thickness of the printe circuit board.15. An electrical connector having a flex circuit which defines an arrayof conductors having contact pads spaced apart in a lateral direction tobe mated with a corresponding array of conductors on a circuit board,comprising:a beam member extending behind the array of flexicircuitconductors in said lateral direction; a compliant member extending insaid lateral direction and directly supported by the beam member,interposed between the beam member and the array of flex circuitconductors to provide compliant sup port for the array of flex circuitconductors; a slot in the beam member on each lateral side of the arrayof flee conductors, said slot having a rigid cam race for engaging a camprofile carried by a circuit board to be joined to the connector;wherein the beam member has a curvature which is convex along saidcompliant member.
 16. The electrical connector of claim 15, wherein eachslot is formed by a cut-out and a distinct clip member supported by thecut-out, said clip defining said cam race.
 17. A method for joining aprinted circuit board having an array of conductors to a connectorhaving a flex circuit with a corresponding array of conductors,comprising:providing at least two posts each having a cam profile, onone of the board or connector, and providing a respective two slots eachdefining a cam race, on the other of the board or connector; advancingthe posts and slots toward each other such that upon partial engagementbetween the posts and slots, the conductors on the board contactrespective conductors on the connector; continuing to advance the postsand slots toward each other that the cam profile on each post interactswith the cam race on a respective slot to produce a predetermined normalcontact force versus advancing position relationship between theconductors in contact, whereby at a fully engaged position of the postsand slots the normal contact force is sufficient to enable signaltransmission through all conductors in contact.
 18. The method of claim17, wherein the step of continuing to advance includes producing anormal contact force that wipes the conductors, before the fully engagedposition is reached.
 19. The method of claim 17, wherein the step ofcontinuing to advance includes advancing to a maximum normal contactforce which is higher than the normal contact force at the fully engagedposition.
 20. The method of claim 17, wherein the step If continuing toadvance includes in sequence, producing a normal contact that wipes theconductors, producing a maximum normal contact force, and then advancingto a fully engaged position at which the normal contact force is lessthan said maximum force.